Internal Waves in the Banda Sea

October 30th, 2015 |
Himawari-8 Band 3 Visible (0.64 µm) images from 29 October [click to play animation]

Himawari-8 Band 3 Visible (0.64 µm) images from 29 October [click to play animation]

Himawari-8 (Imagery courtesy of JMA) captured the northward march of three sets of Internal Waves in the Banda Sea in late October, as shown above (MODIS True Color Imagery showed the waves as well). Because the internal waves affect the ocean surface, sun glint can make them visible via methods described here. The fine spatial and temporal resolution of Himawari-8 (0.5 km for Band 3/0.64µm, 10-minute imagery) allows for a good description of the northward speed of the waves: approximately 10 km/hour.

MTSAT-2 (scheduled to become the backup satellite on Friday 4 December 2015 as Himawari-8 takes over operational duties; MTSAT-1 is to be decommissioned that day because of fuel limitations) and COMS-1 also viewed the waves, as shown below. Sun glint allowed MTSAT-2 to view only three scenes (3:32, 4:32 and 5:32 UTC). COMS-1, above the Equator at 128º E, farther west than MTSAT-2 (at 145º E), viewed the waves earlier (because sunglint was present over the scene earlier). Both MTSAT-2 and COMS-1 visible channels have nominal resolution of only 1 km.

MTSAT-2 Visible (0.73 µm) images from 29 October, 0232-0632 UTC [click to play animation]

MTSAT-2 Visible (0.73 µm) images from 29 October, 0232-0632 UTC [click to play animation]

COMS-1 Visible (0.675 µm) images from 29 October, 0100-0630 UTC [click to play animation]

COMS-1 Visible (0.675 µm) images from 29 October, 0100-0630 UTC [click to play animation]

Hat Tip to Mike Ziobro, NWS Guam, for showing us these very interesting waves!

Explosion in Tianjin, China

August 12th, 2015 |

Himawari-8 (3.9 µm, top), MTSAT-2 (3.75 µm, middle) and COMS-1 (3.75 µm, bottom) shortwave infrared imagery, times as indicated [click to animate]

Himawari-8 (3.9 µm, top), MTSAT-2 (3.75 µm, middle) and COMS-1 (3.75 µm, bottom) shortwave infrared imagery, times as indicated [click to animate]

A storage facility in Tianjin, China exploded shortly after 1500 UTC on 12 August 2015 (media story). Himawari-8, MTSAT-2 and COMS-1 all viewed the explosion that generated a strong thermal signature in the shortwave infrared band (3.75 µm – 3.9 µm). The animation above shows the benefit of Himawari-8’s speedier scanning mode: the smoke clouds that emanate from the explosion are easily traced, and data gaps when Full Disk images are being scanned (around 1800 UTC) are not present. Superior spatial resolution of Himawari-8 infrared channels (2-km, compared to 4-km for COMS-1 and MTSAT-2) means hotter brightness temperatures are sensed as well. The fact that smoke resulting from the explosion was seen spreading northeastward, southeastward, and southwestward was due to a marked shift in wind direction with height, as seen in the nearby Beijing rawinsonde report.

The explosion exhibted a signal in other Himawari-8 AHI bands as well. Band 5, at 1.6 µm and Band 6, at 2.3 µm are shown below (animations courtesy of William Straka, CIMSS); Similar animations are available for 3.9 µm, 6.2 µm (very faintly visible in this upper tropospheric water vapor channel), 7.0 µm, 7.3 µm and 8.6 µm and 10.35 µm.

Himawari-8 1.6 µm near-Infrared Imagery, times as indicated [click to enlarge]

Himawari-8 1.6 µm near-Infrared Imagery, times as indicated [click to animate]

Himawari-8 1.6 µm near-Infrared Imagery, times as indicated [click to animate]

Himawari-8 1.6 µm near-Infrared Imagery, times as indicated [click to animate]

A view of Himawari-8 shortwave IR imagery using the SSEC RealEarth web map server is shown below. In addition, an animation of Himawari-8 true-color images showing the dark smoke plume can be seen here.

Himawari-8 shortwave IR (3.9 um) images, displayed using RealEarth [click to enlarge]

Himawari-8 shortwave IR (3.9 um) images, displayed using RealEarth [click to enlarge]


========================== Added 14 August 2015 ===================

Suomi NPP VIIRS Day/Night Band (0.70 um) visible images on 9 August (before explosion) and 13 August (after explosion) [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.70 um) visible images on 9 August (before explosion) and 13 August (after explosion) [click to enlarge]

The Suomi NPP satellite overflew Tianjin before and after the explosion; VIIRS Day/Night Band images afford views that suggest power outages around the explosion site.

Typhoon Soudelor approaches Taiwan

August 7th, 2015 |
COMS-1 10.8 µm Infrared imagery (click to play animation)

COMS-1 10.8µm Infrared imagery (click to play animation)

Imagery from the Korean COMS-1 satellite, above, shows Category 3 Typhoon Soudelor approaching the island of Taiwan. The eye appearance becomes ragged at the end of the animation, suggesting entrainment of dry air into the center of the Typhoon. Although Sea Surface Temperatures are warm (image taken from here), strengthening before landfall is not forecast. Life-threatening flooding is likely as the circulation and moisture associated with Soudelor interact with the high terrain on the island of Taiwan (Total Precipitable Water animation from MIMIC).

Suomi NPP overflew Soudelor during the morning of the 7th (1709 UTC on 6 August), and the half-moon illumination allowed the VIIRS Day/Night Band to show impressive outflow in the northern semi-circle of the storm; the 11.45 µm Infrared image, however, shows few cold cloud tops just to the north of the eye.

Suomi NPP VIIRS Day/Night Band Visible  (0.70 µm) and Infrared (11.45 µm)  images, 1709 UTC 6 August 2015 (click to enlarge)

Suomi NPP VIIRS Day/Night Band Visible (0.70 µm) and Infrared (11.45 µm) images, 1709 UTC 6 August 2015 (click to enlarge)

A closer view of the eye of Typhoon Soudelor is shown below.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm Infrared images (click to enlarge)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm Infrared images (click to enlarge)

The 16-channel animation from Himawari-8 AHI, below, at half-hour time steps from 0000 through 1230 UTC on 7 August, shows plain evidence of dry air at mid-levels increasing with time, first northeast of the storm and later west of the storm (especially in the ‘water vapor’ channels: 6.2 µm, 6.9 µm and 7.3 µm).

All 16 Himawari-8 AHI channels, 0000-1230 UTC on 7 August, wavelengths as indicated (click to animate)

All 16 Himawari-8 AHI channels, 0000-1230 UTC on 7 August, wavelengths as indicated (click to animate)

About 5 hours prior to landfall on Taiwan, a nighttime comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared (11.45 µm) images at 1653 UTC on 07 August (00:53 AM on 08 August, Taiwan time) is shown below. The images showed a ragged eye structure, but a well-defined spiral band wrapping around the northern semicircle of the typhoon.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared (11.45 µm) images [click to enlarge]

According to The Weather Channel, the highest reported gust in Taiwan was 64.0 meters per second (143 mph) at 5 a.m. Taiwan time on 08 August at Su-ao, Yilan County. However, the Central Weather Bureau deleted all wind data for this site, so the accuracy may be in question. The next-highest gust was 58.5 meters per second (131 mph) on the island of Pengjiayu, northeast of mainland Taiwan. The highest reported rainfall total was 1329.0 millimeters (52.32 inches) at Taipingshan, Datong Township, Yilan County, Taiwan, during the 72-hour period from 06 August through 08 August.

Typhoon Dolphin approaches Guam

May 14th, 2015 |
Himawari-8 11.22 µm infrared channel images (click to play animation)

Himawari-8 11.22 µm infrared channel images (click to play animation)

The animation above (available here as an mp4, and here on YouTube) shows 11.22 µm infrared imagery at 2.5-minute time steps (bottom) and 10-minute time steps (top) from Himawari-8 on 14 May 2015. Category 2 intensity Typhoon Dolphin is approaching Guam, seen at the left edge of both panels in the frame. The 2.5-minute imagery gives a much better indication of the quick rise and decay of overshooting tops (IR brightness temperatures of the storm tops approach -95º C!). A 10-minute time step cannot fully resolve the evolution of these features. The 2.5-minute time step also better captures the divergent flow (and outward-propagating gravity waves) at the top of the central dense overcast. No eye was yet apparent in the infrared imagery, or on DMSP SSMI 85 GHz microwave imagery.

A similar animation from the previous day, 13 May, is shown here: gif, mp4, YouTube. The better organization of the storm on 14 May is readily apparent.

How high are the clouds in the Central Dense Overcast (CDO)? Cloud Heights are available from CLAVR-x (Clouds from AVHRR Extended). Data from Geostationary Satellites are processed and are available to download here. Values from COMS-1 and from MTSAT-2 (displayed with McIDAS-V) suggest maximum cloud heights near 55,500 feet.

The MIMIC Total Precipitable Water (TPW) product, below, showed that Typhoon Dolphin was able to tap rich moisture from the Intertropical Convergence Zone (ITCZ) during the 13-14 May period; TPW values within the tropical cyclone circulation were often in the 60-65 mm or 2.5-2.6 inch range (darker red color enhancement).

MIMIC Total Preciptable Water product (click to play animation)

MIMIC Total Preciptable Water product (click to play animation)

Visible Imagery from Himawari-8, just after sunrise on 15 May, show continuous development of short-lived overshooting tops to the east of Guam. More information on the storm is available at the CIMSS Tropical Cyclones site, the JMA Tropical Cyclone site and the Joint Typhoon Warning Center.

Himawari-8 0.6363 µm visible channel images (click to play animation)

Himawari-8 0.6363 µm visible channel images (click to play animation)